Monday, October 15, 2012

Digesting the Moose Jaw adventure: Part III - Sensory testing for neuropathic pain

Older posts in this series: 

Digesting the Moose Jaw adventure: Part I
Digesting the Moose Jaw adventure: Part II (NERVES, baby..)

Pam Squire is an anesthesiologist in North Vancouver who sits on boards of organizations who endlessly grapple with defining and redefining and classifying and reclassifying the nebulousness of pain. She has many papers listed in pubMed. She is heavily involved in educating and support for organizations dealing with the issues of people living in pain. 

The old idea of neuropathic pain was that it was "pain initiated or caused by a primary lesion or dysfunction in the nervous system". But that simply wasn't adequate to explain a lot of flavours of chronic pain people have that didn't seem to fit into any particular category, so the definition was carefully expanded with new criteria. 
I made a clearer picture of the slide she showed, from Treede et al 2008, Neuropathic pain: redefinition and a grading system for clinical and research purposes: 

Based on 
"Flow chart of grading system for neuropathic pain" 
figure from Treede et al 2008

If "pain" meets the following criteria, it may be considered as "neuropathic":
1. Distinct neuroanatomically plausible distribution. 
2. History suggestive of relevant lesion or disease affecting the peripheral or central somatosensory system.  
3. Demonstration of the distinct neuroanatomically plausible distribution by at least one confirmatory test. 
4. Demonstration of the relevant lesion or disease by at least one confirmatory test. 
If someone has all four indicators they have definite neuropathic pain.
If someone has the first two, and one of the last two, they have probable neuropathic pain. 
If someone has the first two only, they have possible neuropathic pain. 
Neuropathic pain isn't ruled out. It is just a blurrier situation. 

Charting definitive findings is a great idea. It helps people (e.g., insurers) understand what patients are going through. 


Most of the session was on how to do sensory testing. First she gave us each a sensory testing toolkit. 

These simple items are available to anybody. Everybody.

Then she showed us how to use the tools, how to compare one side of the body with the other, little tips on how to help people access the proportional part of their cognition: "If this feels like a dollar... (contact with a toothpick on an intact cutaneous field on the opposite sagittal side of the body).. how much is this worth?..(contact on the affected side with same amount of force)"

She said it was common to get lovely gradated information from this: 60 cents on the elbow, 30 cents on the hand, etc. Quite a good conceptual map could be elicited from the patient's response.

Having patients fill out body diagrams using coloured key identifiers greatly improves the focal length on pain. A different colour for each quality of pain produces a unique map of individual pain that is very helpful to the practitioner - one can see at a glance the patient's pain pattern, how the pain changes over time/treatment, not just in quantity but in quality.

She suggested Yellow for Ache, Red for Sharp, Blue for Burning, Green for Tingling. One could add Purple for Itching, perhaps. She showed some examples; I have manufactured similar examples in colour with photoshop. (Some of her examples can be found in this open access presentation on pain, by her: Workshop)

Arm pain

Shingles pain

I consider this all very useful information, and may actually start tracking this kind of thing a bit more obsessively. Right now, all I use at work is a standard body diagram, filled out by me, mostly to help me remember the patient. But I NOW see that having people map their OWN pain, using colour, would help them interact with their OWN pain better, help them form a clearer cognitive, visual  representation, help them get an idea so they could tackle it better. A copy for them to keep, a copy for the file.

So, thank you Pam Squire!

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